This invention relates to a marine propulsion system, and more particularly to an apparatus and method for improving circulation of lubricant such as oil through the gearcase and drive shaft housing of a stern drive system.
The outboard portion of a stern drive marine propulsion system is broadly defined by a drive shaft housing mounted for pivoting movement about a steering access to the transom of a boat, and a gearcase mounted to the lower end of the drive shaft housing. An input shaft is disposed within an upper cavity provided in the drive shaft housing, and is driven through a universal joint by an inboard mounted internal combustion engine. A bearing assembly is provided in the upper cavity for the input shaft, with the bearings being located adjacent the universal joint.
The input shaft is provided with a drive gear which meshes with forward and reverse gears mounted in the drive shaft housing upper cavity for free rotation about the drive shaft. A clutch assembly is provided on the drive shaft between the forward and reverse gears for selectively coupling the drive shaft to one or the other of such gears. The drive shaft extends downwardly through the drive shaft housing and the gearcase, and is connected at its lower end to a drive gear engaged with a driven gear provided on a propeller shaft, which are disposed in a propeller shaft cavity located in the lower portion of the gearcase.
A top cover is adapted for placement on top of the drive shaft housing, and defines in part the upper wall of the upper cavity in which the input shaft drive gear and the forward and reverse gears are located.
The present invention has as its object to improve oil circulation through the internal cavities and passages provided in the gearcase and the drive shaft housing, and particularly to provide a system in which oil is circulated from the lower portion of the gearcase, which is submerged in the water and cooled during operation, to the upper portion of the drive shaft housing, particularly to the components located in the upper cavity formed therein. Oil from the drive shaft housing upper cavity is circulated down to the gearcase propeller shaft cavity, for cooling the oil prior to its recirculation back up into the drive shaft housing upper cavity. In accomplishing this object of the invention, the life of the universal joint bearing and other components in the drive shaft housing upper cavity is extended due to the supply of cooled oil resulting in reduced operating temperatures.
The invention comprises lubricant circulation means adapted for employment in a marine propulsion system, which may be such as described previously, comprising a housing, an upper input shaft located within a cavity formed in the housing, a drive member mounted to the input shaft, a lower propeller shaft disposed within a propeller shaft cavity, a driven member mounted to the propeller shaft, and drive means extending between the drive member and the driven member for imparting rotation to the propeller shaft in response to rotation of the input shaft. The lubricant circulation means comprises a first supply passage providing communication between the propeller shaft in cavity and the input shaft cavity, including an inlet in the propeller shaft cavity located adjacent the driven member. Rotation of the driven member stimulates a pump-like action on the lubricant to supply lubricant under pressure to the inlet of the first supply passage, with the lubricant flowing therethrough to the input shaft cavity. A return passage communicates between the input shaft cavity and the propeller shaft cavity for providing return flow of lubricant from the input shaft cavity to the propeller shaft cavity. In a system employing a drive shaft having a drive gear at its lower end engaged with a driven gear provided on the propeller shaft, the inlet to the first supply passage is preferably in communication with a space disposed between the forwardmost surface of the driven gear and a rearwardly facing inner surface associated with the propeller shaft cavity, with the lubricant in the space being provided with positive pressure upon rotation of the driven gear. The first supply passage preferably provides unrestricted flow of lubricant from the inlet to a drive shaft housing supply passage, which is in communication with the drive shaft housing upper cavity. In a preferred form of the invention, a bearing supply passage is formed in the drive shaft housing having its inlet in communication with the drive shaft housing supply passage and its outlet disposed adjacent the universal joint. A plug or the like is adapted for placement toward the upper end of the drive shaft housing supply passage, for cutting off communication between the drive shaft housing supply passage and the drive shaft housing upper cavity. In this manner, lubricant pumped through the first supply passage to the drive shaft housing supply passage is directed through the bearing supply passage to the universal joint bearings, where the lubricant first enters the drive shaft housing upper cavity. From the universal joint bearings, the lubricant is supplied to the mesh of the input gear with the forward and reverse gears, and is circularly swirled and pumped by the spinning forward and reverse gears within the portion of the drive shaft housing upper cavity in which such gears are located. A main return passage has its inlet in communication with the drive shaft housing upper cavity, and its outlet in communication with a drive shaft housing return cavity, which provides return flow of lubricant between the drive shaft housing upper cavity and the propeller shaft cavity formed in the lower end of the gearcase.
In accordance with another aspect of the invention, a method of improving lubricant circulation in a marine propulsion system is provided, substantially in accordance with the foregoing description.
In accordance with yet another aspect of the invention, the top cover, which is adapted for placement at the upper end of the drive shaft housing, and defines in part the upper wall of the drive shaft housing upper cavity, is provided with a lubricant inlet in communication with the drive shaft housing upper cavity. A passage extends between the inlet and a recess formed in the lower surface of the top cover, with the recess being adapted to receive the upper end of the drive shaft. In this manner, upon rotation of the uppermost of the upper and lower gears and the pinion by the input shaft lubricant in the upper drive shaft housing cavity is provided under pressure to the inlet of the passage formed in the top cover for supply to the recess, which routes lubricant to the bearings adjacent the upper end of the drive shaft.
In accordance with yet another aspect of the invention, a method of improving oil circulation in the upper cavity of the gearcase comprises providing a top cover substantially in accordance with the foregoing description.
These and other aspects and objects of the invention will be made apparent from the following description taken together with the drawings.